Method and systems for exchanging messages in a wireless network

ABSTRACT

Methods and system for a centralized unit and a distributed unit of a base station to operatively cooperate with each other are disclosed. In one embodiment, a method performed by a first communication node includes: sending a first message to a second wireless communication node upon determining to switch a third wireless communication node to a radio resource control inactive mode. The first and second wireless communication nodes cooperate to serve as a first base station in a wireless network.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 120 asa continuation of PCT Patent Application No PCT/CN2017/104054, filed onSep. 28, 2017, the disclosure of which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The disclosure relates generally to wireless communications and, moreparticularly, to exchanging messages between two wireless communicationnodes in a wireless network.

BACKGROUND

Due to mass connection and higher rate requirements from users in the 5GNew Radio (NR) communication network (5G network), there is a bigchallenge to the transmission capacity of the fronthaul interface CPRI(Common Public Radio Interface) between a BBU (Baseband Unit) and a RRU(Radio Remote Unit) in the LTE (Long-Term Evolution) communicationnetwork. Because the CPRI interface transmits an I/Q (real/imaginary)signal that has been processed by physical layer coding, the CPRIinterface has a tighter requirement on the transmission delay andbandwidth. If the 5G F1 interface rate is increased to tens of giga-bitsper second (Gbps), the traffic demand on the CPRI interface will rise totera-bits per second (Tbps) levels, which will increase both the costand difficulty of network deployment. Therefore, in the 5G network,there is a need to redefine divisions of the fronthaul interface, inconsideration of transmission capacity, transmission delay, ease ofdeployment, and other aspects. For example, taking into account anon-ideal fronthaul transmission, when dividing a base station (BS), onecan put delay-insensitive network functions in a first network element,such as a Centralized Unit (CU), and put delay-sensitive networkfunctions in a second network element, such as a Distributed Unit (DU).There is an ideal and/or non-ideal fronthaul transmission between thefirst and second network element.

Moreover, since the 5G network can support a diverse range ofapplications such as, for example, Massive Machine-Type Communications(M-MTC), Ultra-Reliable and Low Latency Communications (URLLC), EnhancedMobile Broadband (eMBB), etc., it is expected that an increasing numberof user equipment devices (UE's) to be used in some of the aboveapplications will be powered by batteries. Thus, power consumption ofUE's in the 5G network has become one of the anticipated parameters tooptimize or decrease. To this end, and additionally, to reduce signalingoverheads between a random access network (RAN) and a core network (CN)in the 5G network, a new radio resource control (RRC) state, “RRCINACTIVE state,” has been proposed. It is understood that a UE may berequested by a corresponding RAN (e.g., a BS) to switch to the RRCINACTIVE state after the UE has been inactive for a certain period oftime. Different from the known RRC IDLE state, when the UE is in the RRCINACTIVE state, the UE can still move around and process pagingmessages.

To date, however, no research has been conducted regarding how the BS,when divided as CU and DU, switches the UE to the RRC INACTIVE state. Inaddition, when the UE, under the RRC INACTIVE state, moves into a newarea (e.g., a random access network (RAN) notification area), noresearch has been conducted regarding how the CU and DU handle a processto update such a new RAN notification area. Thus, there is a need for amethod and system for the CU and DU to cooperate with each other tohandle such scenarios so as to meet the anticipated demands of the 5Gnetwork.

SUMMARY

The exemplary embodiments disclosed herein are directed to solving theissues relating to one or more of the problems presented in the priorart, as well as providing additional features that will become readilyapparent by reference to the following detailed description when takenin conjunction with the accompany drawings. In accordance with variousembodiments, exemplary systems, methods, devices and computer programproducts are disclosed herein. It is understood, however, that theseembodiments are presented by way of example and not limitation, and itwill be apparent to those of ordinary skill in the art who read thepresent disclosure that various modifications to the disclosedembodiments can be made while remaining within the scope of the presentdisclosure.

In one embodiment, a method performed by a first communication nodeincludes: sending, by the first wireless communication node, a firstmessage to a second wireless communication node upon determining toswitch a third wireless communication node to a radio resource controlinactive mode. The first and second wireless communication nodescooperate to serve as a first base station in a wireless network.

In another embodiment, a method performed by a second communication nodeincludes: receiving a first message sent by a first wirelesscommunication node; and passing a first encoded container included inthe first message to a third wireless communication node, wherein thefirst encoded container is configured to switch the third wirelesscommunication node to a radio resource control inactive mode. The firstand second wireless communication nodes cooperate to serve as a firstbase station in a wireless network.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the invention are described in detailbelow with reference to the following Figures. The drawings are providedfor purposes of illustration only and merely depict exemplaryembodiments of the invention to facilitate the reader's understanding ofthe invention. Therefore, the drawings should not be considered limitingof the breadth, scope, or applicability of the invention. It should benoted that for clarity and ease of illustration these drawings are notnecessarily drawn to scale.

FIG. 1 illustrates an exemplary cellular communication network in whichtechniques disclosed herein may be implemented, in accordance with someembodiments of the invention.

FIG. 2 illustrates a centralized unit-distributed unit (CU-DU)separation structure of a base station of the communication network ofFIG. 1, in accordance with some embodiments of the invention.

FIG. 3 illustrates exemplary functional divisions between a centralizedunit (CU) and a distributed unit (DU) of the base station of FIG. 2, inaccordance with some embodiments.

FIG. 4 illustrates an exemplary block diagram of a centralized unit (CU)of the base station of FIG. 2, in accordance with some embodiments.

FIG. 5 illustrates an exemplary block diagram of a distributed unit (DU)of the base station of FIG. 2, in accordance with some embodiments.

FIG. 6 illustrates a scenario in which the CU and DU of the base stationof FIG. 2 cooperatively perform an exemplary method to switch a userequipment device to an RRC INACTIVE state, in accordance with someembodiments.

FIG. 7 illustrates a scenario in which the CU and DU of the base stationof FIG. 2 cooperatively perform an exemplary method to update a RANnotification area, in accordance with some embodiments.

FIG. 8 illustrates a scenario in which the CU and DU of the base stationof FIG. 2, together with another base station, cooperatively perform anexemplary method to update an RAN notification area, in accordance withsome embodiments.

FIG. 9 illustrates a scenario in which the CU and DU of the base stationof FIG. 2, together with another base station, cooperatively performanother exemplary method to update an RAN notification area, inaccordance with some embodiments.

FIG. 10 illustrates a scenario in which a random access network node(RAN node) and an access and mobility management function (AMF) of acore network cooperatively perform an exemplary method to update alocation of a user equipment device served by the RAN node, inaccordance with some embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Various exemplary embodiments of the disclosure are described below withreference to the accompanying figures to enable a person of ordinaryskill in the art to make and use the disclosure. As would be apparent tothose of ordinary skill in the art, after reading the presentdisclosure, various changes or modifications to the examples describedherein can be made without departing from the scope of the disclosure.Thus, the present disclosure is not limited to the exemplary embodimentsand applications described and illustrated herein. Additionally, thespecific order or hierarchy of steps in the methods disclosed herein aremerely exemplary approaches. Based upon design preferences, the specificorder or hierarchy of steps of the disclosed methods or processes can bere-arranged while remaining within the scope of the present disclosure.Thus, those of ordinary skill in the art will understand that themethods and techniques disclosed herein present various steps or acts ina sample order, and the disclosure is not limited to the specific orderor hierarchy presented unless expressly stated otherwise.

FIG. 1 illustrates an exemplary wireless communication network 100 inwhich techniques disclosed herein may be implemented, in accordance withvarious embodiments of the present disclosure. The exemplarycommunication network 100 includes a base station (BS) 102 and a userequipment device (UE) 104 that can communicate with each other via acommunication link 110 (e.g., a wireless communication channel), and acluster of notional cells 126, 130, 132, 134, 136, 138 and 140overlaying a geographical area 101. In FIG. 1, the BS 102 and UE 104 arecontained within the geographic boundary of cell 126. Each of the othercells 130, 132, 134, 136, 138 and 140 may include at least one basestation operating at its allocated bandwidth to provide adequate radiocoverage to its intended users. For example, the base station 102 mayoperate at an allocated channel transmission bandwidth to provideadequate coverage to the UE 104. The base station 102 and the UE 104 maycommunicate via a downlink radio frame 118, and an uplink radio frame124 respectively. Each radio frame 118/124 may be further divided intosub-frames 120/127 which may include data symbols 122/128. In thepresent disclosure, the base station (BS) 102 and user equipment (UE)104 are described herein as non-limiting examples of “communicationdevices,” generally, which can practice the methods disclosed herein.Such communication devices may be capable of wireless and/or wiredcommunications, in accordance with various embodiments of thedisclosure.

As mentioned above, in the 5G network, a BS may be separated into afirst network element (a centralized network element CU) and a secondnetwork element (a distributed network element DU). FIG. 2 illustrates afronthaul interface between a first network element and a second networkelement of the BS 102, in accordance with some embodiments of thepresent disclosure. As shown, the BS 102 is divided into a first networkelement 210 and a second network element 220. The first network element210 and the second network element 220 communicate through a fronthaulinterface 230, where the fronthaul can be an ideal fronthaul or anon-ideal fronthaul according to different delays. An ideal fronthaultransmission has a relatively small delay, such as tens to hundreds ofmicroseconds. A non-ideal fronthaul transmission has a relatively largedelay, such as milliseconds. Due to the differences between the idealand non-ideal fronthaul transmission, there are different ways to dividedifferent network functions into the first network element 210 and thesecond network element 220.

In one embodiment, the first network element 210 is a CU and the secondnetwork element 220 is a DU, wherein the CU 210 and the DU 220 cancooperate to serve one or more cells as a base station. One CU maycontrol a plurality of DUs at the same time, while a DU can beassociated with one cell or a cell list that includes one or more cells.By controlling a number of DUs with a CU, a wireless system can have abaseband centralized processing and provide distributed remote servicesto users in a cloud architecture.

In a CU-DU separation network architecture, delay-insensitive networkfunctions may be placed in the CU; and delay-sensitive network functionsmay be placed in the DU. Accordingly, a CU and a DU may have differenthardware and structure for implementing the different network functions.

For example, a first protocol entity (e.g., a radio resource control(RRC) entity) is located at the CU. The first protocol entity generatescontrol signals, maintains the establishment, modification, and/orrelease of the radio bearer, and maintains updated parameters of asecond protocol entity, a third protocol entity, a fourth protocolentity, and the physical (PHY) layer of the base station. The secondprotocol entity has a similar or enhanced function compared to the PDCP(Packet Data Convergence Protocol) function of an LTE system. The thirdprotocol entity has a similar or enhanced function compared to the RLC(Radio Link Control) function of an LTE system. The fourth protocolentity has a similar or enhanced function compared to the MAC (MediumAccess Control) function of an LTE system. The DU comprises at least oneof: the second protocol entity, the third protocol entity, the fourthprotocol entity, the physical layer, and the radio frequency (RF) unitof the base station.

FIG. 3 illustrates exemplary functional divisions between the firstnetwork element and the second network element, e.g. between the CU 210and the DU 220, in accordance with some embodiments of the presentdisclosure. More specifically, FIG. 3 illustrates eight possiblefunctional division options between the CU 210 and the DU 220, which arerespectively described below.

Option 1 (RRC/PDCP separation): The functional separation of this optionis similar to the 1A structure in a dual connection (DC). RRC is locatedwithin CU; PDCP, RLC, MAC, PHY and RF functions are located in DU. Thatis, the entire UP is located in DU.

Option 2 (PDCP/RLC separation): The functional separation of this optionis similar to the 3C structure in a dual connection (DC). RRC and PDCPare located within CU; RLC, MAC, PHY and RF functions are located in DU.

Option 3 (RLC high-level/low-level separation): The low-level RLC(partial function of the RLC), MAC, PHY, and RF are located within DU;RRC, PDCP and high-level RLC (partial function of the RLC) functions arelocated in the CU.

Option 4 (RLC-MAC separation): MAC, PHY and RF parts are located withinDU; PDCP and RLC functions are located in the CU.

Option 5 (MAC internal separation): Some of the MAC functions (such asHARQ), PHY and RF are located in DU; the other upper level functions arelocated in the CU.

Option 6 (MAC-PHY): PHY and RF parts are located in DU; RRC, PDCP, RLCand MAC functions are located in the CU.

Option 7 (PHY internal separation): Some of the PHY functions and RF arelocated in DU; the other upper function is located in the CU.

Option 8 (PHY-RF separation): The RF part is located within the DU; andthe other upper level functions are located in the CU.

In one embodiment, when a standard supports two or more options fordividing network functions into CU and DU, the wireless system canadaptively switch between the supported options during wirelesscommunications.

FIG. 4 illustrates an exemplary block diagram of the CU 210, inaccordance with some embodiments of the present disclosure. The CU 210is an example of a device that can be configured to implement variousmethods described, as will be discussed below. As shown, the CU 210includes a housing 401 comprising: a system clock 402, a processor 404,a memory 406, a transceiver 410 comprising a transmitter 412 and areceiver 414, a power module 408, and a CU network connection module420. In some embodiments, the above-mentioned components/modules arecoupled together by a bus system 424. The bus system 424 can include adata bus and, for example, a power bus, a control signal bus, and/or astatus signal bus in addition to the data bus. It is understood that thecomponents/modules of the CU 210 can be operatively coupled to oneanother using any suitable techniques and mediums.

In some embodiments, the system clock 402 provides the timing signals tothe processor 404 for controlling the timing of all operations of the CU210. The processor 404 controls the general operation of the CU 210 andcan include one or more processing circuits or modules such as a centralprocessing unit (CPU) and/or any combination of general-purposemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate array (FPGAs), programmable logic devices(PLDs), controllers, state machines, gated logic, discrete hardwarecomponents, dedicated hardware finite state machines, or any othersuitable circuits, devices and/or structures that can performcalculations or other manipulations of data.

The memory 406, which can include both read-only memory (ROM) and randomaccess memory (RAM), can provide instructions and data to the processor404. A portion of the memory 406 can also include non-volatile randomaccess memory (NVRAM). The processor 404 typically performs logical andarithmetic operations based on program instructions stored within thememory 406. The instructions (a.k.a., software) stored in the memory 406can be executed by the processor 404 to perform the methods describedherein. The processor 404 and memory 406 together form a processingsystem that stores and executes software. As used herein, “software”means any type of instructions, whether referred to as software,firmware, middleware, microcode, etc. which can configure a machine ordevice to perform one or more desired functions or processes.Instructions can include code (e.g., in source code format, binary codeformat, executable code format, or any other suitable format of code).The instructions, when executed by the one or more processors, cause theprocessing system to perform the various functions described herein.

The transceiver 410, which includes the transmitter 412 and receiver414, allows the CU 210 to transmit and receive data to and from a remotedevice (e.g., a DU). In one embodiment, an antenna 422 may be attachedto the housing 401 and electrically coupled to the transceiver 410. Invarious embodiments, the CU 210 includes (not shown) multipletransmitters, multiple receivers, multiple transceivers, and/or multipleantennas. The transmitter 412 can be configured to wirelessly transmitpackets having different packet types or functions, such packets beinggenerated by the processor 404. Similarly, the receiver 414 isconfigured to receive packets having different packet types orfunctions, and the processor 404 is configured to process packets of aplurality of different packet types. For example, the processor 404 canbe configured to determine the type of packet and to process the packetand/or fields of the packet accordingly. In another embodiment, the CU210 may communicate with a DU via fiber-optic communication, such thatthe transmitter 412 and the receiver 414 can be configured to transmitand receive signals respectively through an optical fiber.

The power module 408 can include a power source such as one or morebatteries, and a power regulator, to provide regulated power to each ofthe above-described modules in FIG. 4. In some embodiments, if the CU210 is coupled to a dedicated external power source (e.g., a wallelectrical outlet), the power module 408 can include a transformer and apower regulator.

The CU network communication module 420 generally represents thehardware, software, firmware, processing logic, and/or other componentsof the CU 210 that enable bi-directional communication between thetransceiver 410 and other network components and communication devicesconfigured to communication with the CU 210 (e.g., the DU 220). Forexample, the CU network communication module 420 may generate a messagethat comprises various information associated with the DU 220 and/or aUE that is cooperatively served by the CU 210 and DU 220. The CU networkcommunication module 420 may send the message to the transmitter 412,and instruct the transmitter 412 to transmit the message to the DU 220associated with the CU 210, where the CU 210 and the DU 220 cancooperate to serve as a first base station in a wireless network, and/oranother CU that cooperates with at least one corresponding DU to serveas a second base station in the wireless network. Detailed operations ofthe CU 210 will be discussed in further detail below.

FIG. 5 illustrates an exemplary block diagram of the DU 220, inaccordance with some embodiments of the present disclosure. The DU 220is an example of a device that can be configured to implement variousmethods described, as will be discussed below. Similarly with the CU 210shown in FIG. 4, the DU 220 includes a housing 501 comprising: a systemclock 502, a processor 504, a memory 506, a transceiver 510 comprising atransmitter 512 and a receiver 514, a power module 508, and a DU networkconnection module 520, wherein the above components/modules are coupledtogether by a bus system 524. In some embodiments, respectivefunctionalities of the components/modules of the DU 220 (e.g., 502, 504,506, 508, 510, and 522) are substantially similar to correspondingcomponents/modules of the CU 210 except for the DU network connectionmodule 520. Thus, the components/modules 502-522 are not repeated here.

The DU network communication module 520 generally represents thehardware, software, firmware, processing logic, and/or other componentsof the DU 220 that enable bi-directional communication between thetransceiver 510 and other network components and communication devicesconfigured to communication with the DU 220 (e.g., the CU 210). Forexample, the DU network communication module 520 may process a messagethat comprises various information associated with the DU 220 itselfand/or the above-mentioned UE. The DU network communication module 520may send the message to the transmitter 512, and instruct thetransmitter 512 to transmit the message to the CU 210, and/or the UE.Detailed operations of the DU 220 will be discussed in further detailbelow. The terms “configured for,” “configured to” and conjugationsthereof, as used herein with respect to a specified operation orfunction, refer to a device, component, circuit, structure, machine,signal, etc., that is physically constructed, programmed, formattedand/or arranged to perform the specified operation or function.

Referring again to FIGS. 1 and 2, as discussed above, the UE 104 may beinstructed to switch to the RRC INACTIVE state in order to reduce powerconsumption of the UE 104 and signaling overheads. The presentdisclosure provides various embodiments of systems and methods toillustrate how the CU 210 and DU 220 of the BS 102 operatively cooperateto cause the UE 104 to switch to the RRC INACTIVE state. After the UE104 switches to the RRC INACTIVE state and moves into a new area (e.g.,an RAN notification area), the disclosed embodiments further illustratehow the CU 210 and DU 220 operatively cooperate to update the area wherethe UE has moved to. Still further, the disclosed embodiments illustratehow the CU 210 reports a current area where the UE 104 is located, whichcan be the aforementioned RAN notification area, to a core network uponrequest.

FIG. 6 illustrates a scenario in which the CU 210 and DU 220cooperatively perform a method 600 to switch the UE 104 to the RRCINACTIVE state, in accordance with some embodiments. The method 600starts with operation 602 in which the CU 210 sends a downlink radioresource control (DL RRC) message to the DU 220. In some embodiments,the CU 210 may send the DL RRC message to one or more associated DUs(e.g., 220) upon determining to switch the UE 104 to the RRC INACTIVEstate due to various concerns, as discussed above.

In some embodiments, the DL RRC message may include at least one of thefollowing information: an encoded container including a suspend signal,a flag signal indicative of deleting a context of the UE 104 (e.g., UE104's capability, identifier, etc.) that was previously stored in the DU220, a cell-radio network temporary identifier (C-RNTI) that the DU 220previously assigned to the UE 104, a first application identifier (APID) over the fronthaul interface (e.g., the F1 interface) between the CU210 and DU 220 that the DU 220 previously assigned to the UE 104(typically known as “DU F1 UE AP ID”), an optional second AP ID over theF1 interface between the CU 210 and DU 220 that the CU 210 previouslyassigned to the UE 104 (typically known as “CU F1 UE AP ID”), and asignaling radio bearer (SRB) type.

In some embodiments, the suspend signal is an F1 interface signalconfigured to cause the UE 104 to switch to the RRC INACTIVE state. Insome embodiments, the CU 210 may encode the suspend signal in thecontainer. More specifically, the container including the suspend signalmay be encoded at an RRC layer, which is accordingly referred to as an“RRC container,” and when the DU 220 and UE 104 respectively receive theRRC container, as will be discussed below, the DU 220 does not need todecode the RRC container; but the UE 104 which also include acorresponding RRC layer, can decode the RRC container to obtain thesuspend signal.

Next, the method 600 continues to operation 604 in which the DU 220deletes the context of the UE 104. In some embodiments, when the DU 220receives the DL RRC message, based on the flag signal included in the DLRRC message, the DU 220 determines whether to delete the context of theUE 104. For example, when the flag signal is at a first logic state(e.g., a logic 1), the DU 220 may delete the context of the UE 104; andwhen the flag signal is at a second logic state (e.g., a logic 0), theDU 220 may keep the context of the UE 104.

Next, the method 600 continues to operation 606 in which the DU 220passes the RRC container included in the DL RRC message to the UE 104.As mentioned above, in some embodiments, when the DU 220 receives the DLRRC message, the DU 220 does not decode the RRC container carrying thesuspend signal (i.e., passing the container directly to the UE 104). Assuch, when the UE 104 receives the RRC container, the UE 104 decodes theRRC container to retrieve the suspend signal so as to switch itself tothe RRC INACTIVE state.

FIG. 7 illustrates a scenario in which the CU 210 and DU 220cooperatively perform a method 700 to update an RAN notification areawhere the UE 104 has moved to, in accordance with some embodiments. Insome embodiments, when the UE 104 is under the RRC INACTIVE state, sucha process to update the RAN notification area of the UE 104 may bereferred to as a random access update (RAU) process. Further, in someembodiments, during such an RAU process, a link over an interfacebetween the CU 210 and an access and mobility management function (AMF)of a core network (e.g., an NG interface) may remain intact.

The method 700 starts with operation 702 in which the UE 104 sends arandom access update (RAU) message to the DU 220. In some embodiments,the UE 104 encodes the RAU message at the RRC layer, and sends the RAUmessage upon requesting to update a respective RAN notification area. Asmentioned above, when the UE 104 is under the RRC INACTIVE state, the UE104 may move around. When the UE 104 moves into a new RAN notificationarea, by receiving system information broadcasted in that new RANnotification area, the UE 104 may determine that it has entered into adifferent RAN notification area. In some embodiments, the UE 104 maysend such an RAU message to the DU 220 that serves the new RANnotification area. As such, the new RAN notification area may be stillserved by the CU 210.

Next, the method 700 continues to operation 704 in which the DU 220sends an uplink radio resource control (UL RRC) message to the CU 210.In some embodiments, the DU 220 may send such an UL RRC message uponreceiving the RAU message from one or more UEs (e.g., UE 104).

In some embodiments, the UL RRC message may include at least one of thefollowing information: a encoded container including the RAU message(hereinafter “RRC RAU container”), a cell-radio network temporaryidentifier (C-RNTI) that the DU 220 previously assigned to the UE 104,an application identifier (AP ID) over the fronthaul interface (e.g., F1interface) between the CU 210 and DU 220 that the DU 220 previouslyassigned to the UE 104 (typically known as “DU F1 UE AP ID”), and asignaling radio bearer (SRB) type. In some embodiments, the RRC RAUcontainer may be processed (e.g., encoded) by and then sent from the UE104. Similarly, the DU 220 does not decode the RRC RAU container, butpasses the RRC RAU container to the CU 210. In some embodiments, the DUF1 UE AP ID, as discussed herein, may be identical to the DU F1 UE AP IDdiscussed with respect to FIG. 6.

Next, the method 700 continues to operation 706 in which the CU 210sends a DL RRC message to the DU 220. In some embodiments, uponreceiving the RRC RAU container included in the UL RRC message, the CU210 decodes the RRC RAU container to retrieve the RAU message. Whensuccessfully decoding the RAU message, the CU 210 sends the DL RRCmessage (hereinafter “successful DL RRC message”) to the DU 220; and onthe other hand, when unsuccessfully decoding the RAU message, the CU 210sends another DL RRC message (“unsuccessful DL RRC message”) to the DU220, which will be respectively discussed below.

In some embodiments, the successful DL RRC message includes at least oneof the following information: an encoded container including an areaupdate acknowledgement RRC message (hereinafter “RRC RAU ACK container”and “RAU ACK message,” respectively), the C-RNTI that the DU 220previously assigned to the UE 104, the DU F1 UE AP ID that the DU 220previously assigned to the UE 104, an optional AP ID over the F1interface between the CU 210 and DU 220 that the CU 210 previouslyassigned to the UE 104 (typically known as “CU F1 UE AP ID”), and a flagsignal indicative of deleting a context of the UE 104 (e.g., UE 104'scapability, identifier, etc.) that was previously stored in the DU 220.In some embodiments, the CU F1 UE AP ID, as discussed herein, may beidentical to the CU F1 UE AP ID discussed with respect to FIG. 6.

In some embodiments, the unsuccessful DL RRC message includessubstantially similar information as the successful DL RRC message doesexcept that, instead of the RRC RAU ACK container, the unsuccessful DLRRC message includes a different encoded container including an RRCrelease message (hereinafter “RRC release container”). The RRC releasemessage may be generated by the CU 210 so as to cause the UE 104 toswitch to an RRC IDLE state (i.e., releasing all, or substantially all,RRC resources).

According to some embodiments, since the successful and unsuccessful DLRRC messages each includes the flag signal, regardless of whether thesuccessful or unsuccessful DL RRC message is received by the DU 220, theDU 220 may delete the context of the UE 104 that was stored in the DU220 based on a logic state of the flag signal (as described above).

In some embodiments, when in the operation 706, the CU 210 sends thesuccessful DL RRC message, including the RRC RAU ACK container, themethod 700 continues to operation 708 in which the DU 220 passes the RRCRAU ACK container to the UE 104. Similar to other containers describedabove, the DU 220 does not decode the RRC RAU ACK container, but the UE104 decodes the RRC RAU ACK container to retrieve the included RAU ACKmessage. Accordingly, the RAU process, initiated by the UE 104, may becompleted. On the other hand, when in the operation 706, the CU 210sends the unsuccessful DL RRC message including the RRC releasecontainer, the DU 220 may pass the RRC release container to the UE 104in the operation 708, and similarly, the UE 104 may decode the RRCrelease message from the RRC release container so as to cause itself toswitch to the RRC IDLE state.

FIG. 8 illustrates a scenario in which the CU 210 and DU 220 (serving asthe BS 102) and another pair of CU 810 and DU 820 serving as another BS,different from the BS 102, cooperatively perform a method 800 to updatean RAN notification area where the UE 104 has moved to, in accordancewith some embodiments. Different from the scenario illustrated in FIG. 7in which the new RAN notification area that the UE 104 moves into isstill served by the same CU 210, in the scenario of FIG. 8, the UE 104may move into a new RAN notification area that is not served by the CU210. As such, an RAU process may be initiated by the UE 104. However,similar to the scenario of FIG. 7, during the RAU process of FIG. 8, alink over the interface between the CU 210 and the access and mobilitymanagement function (AMF) of the core network (e.g., an NG interface)may remain intact.

The method 800 starts with operation 801 in which the UE 104 sends arandom access update (RAU) message to the DU 820. In some embodiments,the UE 104 encodes the RAU message at the RRC layer, and sends the RAUmessage upon requesting to update a respective RAN notification area. Asmentioned above, when the UE 104 is under the RRC INACTIVE state, the UE104 may move around. When the UE 104 moves into a new RAN notificationarea, by receiving system information broadcasted in that new RANnotification area, the UE 104 may determine that it has entered into adifferent RAN notification area. In some embodiments, the UE 104 maysend such an RAU message to the DU 820 that serves the new RANnotification area. As such, the new RAN notification area may be servedby the CU 810 instead of the CU 210.

Next, the method 800 continues to operation 803 in which the DU 820sends an uplink radio resource control (UL RRC) message to thecorresponding CU 810. In some embodiments, the DU 820 may send such anUL RRC message upon receiving the RAU message from one or more UEs(e.g., UE 104).

In some embodiments, the UL RRC message may include at least one of thefollowing information: a encoded container including the RAU message(hereinafter “RRC RAU container”), a cell-radio network temporaryidentifier (C-RNTI) that the DU 820 previously assigned to the UE 104,an application identifier (AP ID) over the fronthaul interface (e.g., F1interface) between the DU 810 and DU 820 that the DU 820 previouslyassigned to the UE 104 (typically known as “DU F1 UE AP ID”), and asignaling radio bearer (SRB) type. In some embodiments, the RRC RAUcontainer may be processed (e.g., encoded) by and then sent from the UE104. Similarly, the DU 820 does not decode the RRC RAU container, butpasses the RRC RAU container to the CU 810. In some embodiments, the DUF1 UE AP ID, as discussed herein, may be identical to the DU F1 UE AP IDdiscussed with respect to FIG. 6.

Next, the method 800 continues to operation 805 in which the CU 810sends the RAU message to the CU 210 over an interface between the CU 810and the CU 210 (e.g., an Xn interface). In some embodiments, uponreceiving the RRC RAU container, the CU 810 decodes the RRC RAUcontainer to retrieve the RAU message, and sends the RAU message to theCU 210. In some embodiments, the RAU message may be sent over the Xninterface using an application layer. Next, the method 800 continues tooperation 807 in which the CU 210 sends an area update acknowledgementRRC message (hereinafter “RAU ACK message”) to the CU 810. In someembodiments, when the CU 210 successfully processes the RAU message anddetermines that the CU 210 remains serving as an anchor point to thecore network (i.e., still holding the context of the UE 104), the CU 210sends the RAU ACK message to the CU 810. Similarly, the RAU ACK messagemay be sent over the Xn interface using the application layer. Similarto the operation 706 of the method 700 of FIG. 7, when the CU 210unsuccessfully processes the RAU message, the CU 210 may send an updatefailure message to the CU 810, and the CU 810 generates an RRC releasemessage to cause the UE 104 to switch to the RRC IDLE state, which isnot repeatedly discussed here.

Next, the method 800 continues to operation 809 in which the CU 810sends a DL RRC message to the DU 820. In some embodiments, uponreceiving the RAU ACK message, the CU 810 sends the DL RRC message tothe DU 820. In some embodiments, the DL RRC message includes at leastone of the following information: an encoded container including the RAUACK message (hereinafter “RRC RAU ACK container”), the C-RNTI that theDU 820 previously assigned to the UE 104, the DU F1 UE AP ID that the DU820 previously assigned to the UE 104, an optional AP ID over the F1interface between the CU 810 and DU 820 that the CU 810 previouslyassigned to the UE 104 (typically known as “CU F1 UE AP ID”), and a flagsignal indicative of deleting a context of the UE 104 (e.g., UE 104'scapability, identifier, etc.) that was previously stored in the DU 820.In some embodiments, upon receiving the flag signal, the DU 820 maydelete the context of the UE 104 that was stored in the DU 820 based ona logic state of the flag signal (as described above). In someembodiments, the CU F1 UE AP ID, as discussed herein, may be identicalto the CU F1 UE AP ID discussed with respect to FIG. 6.

Next, the method 800 continues to operation 811 in which the DU 820passes the RRC RAU ACK container to the UE 104. Similar to othercontainers described above, the DU 820 does not decode the RRC RAU ACKcontainer, but the UE 104 decodes the RRC RAU ACK container to retrievethe included RAU ACK message. Accordingly, the RAU process, initiated bythe UE 104, may be completed.

FIG. 9 illustrates a scenario in which the CU 210 and DU 220 (serving asthe BS 102) and another pair of CU 910 and DU 920 serving as another BS,different from the BS 102, cooperatively perform a method 900 to updatean RAN notification area where the UE 104 has moved to, in accordancewith some embodiments. The scenario of FIG. 9 is substantially similarto the scenario of FIG. 8 except that, in FIG. 9, the CU 910 replacesthe CU 210 serving as the new anchor point to the core network.Accordingly, the reference numerals of the method 800 are respectivelyincremented by 100 to be used in the method 900. It is noted thatoperations 901 to 911 are respectively identical to the operations 801to 811 except for the operation 907. More specifically, since the CU 210does not serve as the anchor point, when the CU 210 sends the RAU ACKmessage to the CU 910 during the operation 907 in the method 900, theRAU ACK message may further include the context of the UE 104.Alternatively stated, the context of the UE 104 is “transferred” fromthe CU 210 to the CU 910. In some embodiments, the CU 210 may determinewhether itself still serves as the anchor point during the operation 907of the method 900.

Similarly, in some embodiments, during the RAU process as illustrated inthe scenario of FIG. 9, a link over an interface between the CU 210 andan access and mobility management function (AMF) of a core network(e.g., an NG interface) may remain intact. However, since the CU 910 hasreplaced the CU 210 as the new anchor point to the core network, it isunderstood by persons of ordinary skill in the art that the AMF (notshown) and the CU 910 may exchange one or more messages to update a datacommunication route.

FIG. 10 illustrates a scenario in which a random access network node(RAN node) and an access and mobility management function (AMF) of acore network cooperatively perform a method 1000 to update a location ofa UE served by the RAN node, in accordance with some embodiments. It isunderstood that the RAN node, as described herein, can be a gNB, an eNBconnected to the AMF, a CU of a BS, etc.

The method 1000 starts with operation 1002 in which the AMF requests toreport a location of the UE. In some embodiments, the AMF may send afirst message over the NG interface to the RAN node requesting to updatethe location of the UE. In some embodiments, the first message mayinclude at least one of the following information: an identifier of theUE over the NG interface, a report type, and a report resolution. In anembodiment, the report type may include an RRC INACTIVE type.Specifically, when the UE switches to the RRC INACTIVE state andinitiates an area update process (e.g., the RAU process) after movinginto a new area, the RAN node is requested to report the location of theUE. And the report resolution may include a resolution of a cell, aresolution of an RAN notification area, etc.

Next, the method 1000 continues to operation 1004 in which the RAN nodereports the location of the UE. In some embodiments, after the RAN nodesuccessfully processes the first message, the RAN node may send a secondmessage back to the AMF to report the location of the UE. In someembodiments, the second message may include at least one of thefollowing information: the identifier of the UE over the NG interface, alast updated location of the UE when the UE is under the RRC INACTIVEstate, etc. Specifically, the location of the UE can be indicated by: acell global identifier, a tracking area identifier, an RAN notificationarea identifier.

The method 1000 proceeds to operation 1004 in which the RAN node failsto report the location of the UE. In some cases, the RAN node mayunsuccessfully process the first message. As such, the RAN node may senda third message back to the AMF indicating that the update on thelocation of the UE has failed. It is noted that the operation 1004 maynot necessarily occur subsequently to the operation 1002.

While various embodiments of the invention have been described above, itshould be understood that they have been presented by way of exampleonly, and not by way of limitation. Likewise, the various diagrams maydepict an example architectural or configuration, which are provided toenable persons of ordinary skill in the art to understand exemplaryfeatures and functions of the invention. Such persons would understand,however, that the invention is not restricted to the illustrated examplearchitectures or configurations, but can be implemented using a varietyof alternative architectures and configurations.

Additionally, as would be understood by persons of ordinary skill in theart, one or more features of one embodiment can be combined with one ormore features of another embodiment described herein. Thus, the breadthand scope of the present disclosure should not be limited by any of theabove-described exemplary embodiments.

It is also understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations can be used herein as a convenient means of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements can be employed, or that the first element must precede thesecond element in some manner.

Additionally, a person having ordinary skill in the art would understandthat information and signals can be represented using any of a varietyof different technologies and techniques. For example, data,instructions, commands, information, signals, bits and symbols, forexample, which may be referenced in the above description can berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

A person of ordinary skill in the art would further appreciate that anyof the various illustrative logical blocks, modules, processors, means,circuits, methods and functions described in connection with the aspectsdisclosed herein can be implemented by electronic hardware (e.g., adigital implementation, an analog implementation, or a combination ofthe two), firmware, various forms of program or design codeincorporating instructions (which can be referred to herein, forconvenience, as “software” or a “software module), or any combination ofthese techniques. To clearly illustrate this interchangeability ofhardware, firmware and software, various illustrative components,blocks, modules, circuits, and steps have been described above generallyin terms of their functionality. Whether such functionality isimplemented as hardware, firmware or software, or a combination of thesetechniques, depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans canimplement the described functionality in various ways for eachparticular application, but such implementation decisions do not cause adeparture from the scope of the present disclosure.

In accordance with various embodiments, a processor, device, component,circuit, structure, machine, module, etc. can be configured to performone or more of the functions described herein. The term “configured to”or “configured for” as used herein with respect to a specified operationor function refers to a processor, device, component, circuit,structure, machine, module, etc. that is physically constructed,programmed and/or arranged to perform the specified operation orfunction.

Furthermore, a person of ordinary skill in the art would understand thatvarious illustrative logical blocks, modules, devices, components andcircuits described herein can be implemented within or performed by anintegrated circuit (IC) that can include a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, or any combination thereof. The logicalblocks, modules, and circuits can further include antennas and/ortransceivers to communicate with various components within the networkor within the device. A general purpose processor can be amicroprocessor, but in the alternative, the processor can be anyconventional processor, controller, or state machine. A processor canalso be implemented as a combination of computing devices, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other suitable configuration to perform the functionsdescribed herein.

If implemented in software, the functions can be stored as one or moreinstructions or code on a computer-readable medium. Thus, the steps of amethod or algorithm disclosed herein can be implemented as softwarestored on a computer-readable medium. Computer-readable media includesboth computer storage media and communication media including any mediumthat can be enabled to transfer a computer program or code from oneplace to another. A storage media can be any available media that can beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media can include RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer.

In this document, the term “module” as used herein, refers to software,firmware, hardware, and any combination of these elements for performingthe associated functions described herein. Additionally, for purpose ofdiscussion, the various modules are described as discrete modules;however, as would be apparent to one of ordinary skill in the art, twoor more modules may be combined to form a single module that performsthe associated functions according embodiments of the invention.

Additionally, memory or other storage, as well as communicationcomponents, may be employed in embodiments of the invention. It will beappreciated that, for clarity purposes, the above description hasdescribed embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits, processing logic elements or domains may be used withoutdetracting from the invention. For example, functionality illustrated tobe performed by separate processing logic elements, or controllers, maybe performed by the same processing logic element, or controller. Hence,references to specific functional units are only references to asuitable means for providing the described functionality, rather thanindicative of a strict logical or physical structure or organization.

Various modifications to the implementations described in thisdisclosure will be readily apparent to those skilled in the art, and thegeneral principles defined herein can be applied to otherimplementations without departing from the scope of this disclosure.Thus, the disclosure is not intended to be limited to theimplementations shown herein, but is to be accorded the widest scopeconsistent with the novel features and principles disclosed herein, asrecited in the claims below.

What is claimed is:
 1. A method performed by a first wirelesscommunication node, comprising: sending, by the first wirelesscommunication node, a first message to a second wireless communicationnode upon determining to switch a third wireless communication node to aradio resource control inactive mode, wherein the first and secondwireless communication nodes cooperate to serve as a first base stationin a wireless network, wherein the first message comprises at least oneof: a first encoded container comprising a suspend signal, a flag signalindicative of deleting a context of the third wireless communicationnode that was stored in the second wireless communication node, acell-radio network temporary identifier that the second wirelesscommunication node assigned to the third wireless communication node, afirst application identifier over an F1 interface between the first andsecond wireless communication nodes that the second wirelesscommunication node assigned to the third wireless communication node, asecond application identifier over the F1 interface between the firstand second wireless communication nodes that the first wirelesscommunication node assigned to the third wireless communication node, ora signaling radio bearer type, wherein the second wireless communicationnode is configured to pass the first encoded container to the thirdwireless communication node for the third wireless communication node toretrieve the suspend signal from the first encoded container so as toswitch itself to the radio resource control inactive mode.
 2. The methodof claim 1, wherein the first wireless communication node is acentralized unit of the first base station, and the second wirelesscommunication node is a distributed unit of the first base station. 3.The method of claim 1, further comprising: when the third wirelesscommunication node switches to the radio resource control inactive mode,receiving, by the first wireless communication node, a second messagefrom the second wireless communication node indicating that the thirdwireless communication node has sent a radio resource control message tothe second wireless communication node requesting to update a respectiverandom access network notification area.
 4. The method of claim 3,wherein the second message comprises at least one of the followinginformation: a second encoded container comprising the radio resourcecontrol message, the cell-radio network temporary identifier that thesecond wireless communication node assigned to the third wirelesscommunication node, the first application identifier over the F1interface between the first and second wireless communication nodes thatthe second wireless communication node assigned to the third wirelesscommunication node, and the signaling radio bearer type.
 5. The methodof claim 4, further comprising: retrieving the radio resource controlsignal from the second encoded container; and in response tosuccessfully decoding the radio resource control signal, sending a thirdmessage to the second wireless communication node, wherein the thirdmessage comprises at least one of the following information: a thirdencoded container comprising an area update acknowledgement radioresource control message, the cell-radio network temporary identifierthat the second wireless communication node assigned to the thirdwireless communication node, the first application identifier over theF1 interface between the first and second wireless communication nodesthat the second wireless communication node assigned to the thirdwireless communication node, the flag signal indicative of deleting thecontext of the third wireless communication node that was stored in thesecond wireless communication node, and the second applicationidentifier over the F1 interface between the first and second wirelesscommunication nodes that the first wireless communication node assignedto the third wireless communication node.
 6. The method of claim 5,wherein the second wireless communication node is configured to pass thethird encoded container to the third wireless communication node for thethird wireless communication node to retrieve the area updateacknowledgement radio resource control message from the third encodedcontainer.
 7. The method of claim 5, further comprising: whenunsuccessfully decoding the radio resource control signal, sending afourth message to the second wireless communication node, wherein thefourth message comprises at least one of the following information: afourth encoded container comprising a radio resource control releasemessage, the cell-radio network temporary identifier that the secondwireless communication node assigned to the third wireless communicationnode, the first application identifier over the F1 interface between thefirst and second wireless communication nodes that the second wirelesscommunication node assigned to the third wireless communication node,the flag signal indicative of deleting the context of the third wirelesscommunication node that was stored in the second wireless communicationnode, and the second application identifier over the F1 interfacebetween the first and second wireless communication nodes that the firstwireless communication node assigned to the third wireless communicationnode.
 8. The method of claim 1, further comprising: when the thirdwireless communication node switches to the radio resource controlinactive mode, receiving, by the first wireless communication node, arandom access network notification update message from a fourth wirelesscommunication node, wherein the random access network notificationupdate message is generated based on a radio resource control messagethat is sent by the third wireless communication node to a fifthwireless communication node requesting to update a respective randomaccess network notification area, and wherein the fourth wirelesscommunication node is a centralized unit of a second base station in thewireless network but different from the first base station, and thefifth wireless communication node is a distributed unit of the secondbase station.
 9. The method of claim 8, further comprising: in responseto successfully processing the random access network notification updatemessage and determining that the first wireless communication noderemains serving as an anchor point to a core network, sending a fifthmessage to the fourth wireless communication node, wherein the fifthmessage comprises an area update acknowledgement radio resource controlmessage.
 10. The method of claim 9, wherein in response to receiving thefifth message, the fourth wireless communication node sends a sixthmessage to the fifth wireless communication node, and wherein the sixthmessage comprises at least one of the following information: a fifthencoded container comprising the area update acknowledgement radioresource control message, a cell-radio network temporary identifier thatthe fifth wireless communication node assigned to the third wirelesscommunication node, a first application identifier over an F1 interfacebetween the fourth and fifth wireless communication nodes that the fifthwireless communication node assigned to the third wireless communicationnode, a second application identifier over the F1 interface between thefourth and fifth wireless communication nodes that the fourth wirelesscommunication node assigned to the third wireless communication node,and a flag signal indicative of deleting a context of the third wirelesscommunication node that was stored in the fifth wireless communicationnode.
 11. The method of claim 9, further comprising: in response tosuccessfully processing the random access network notification updatemessage and determining that the fourth wireless communication node hasreplaced the first wireless communication node serving as the anchorpoint to the core network, sending a seventh message to the fourthwireless communication node, wherein the seventh message comprises thearea update acknowledgement radio resource control message and thecontext of the third wireless communication node that was stored in thesecond wireless communication node.
 12. The method of claim 11, whereinin response to receiving the seventh message, the fourth wirelesscommunication node sends an eighth message to the fifth wirelesscommunication node, and wherein the eighth message comprises at leastone of the following information: a sixth encoded container comprisingthe area update acknowledgement radio resource control message, acell-radio network temporary identifier that the fifth wirelesscommunication node assigned to the third wireless communication node, afirst application identifier over an F1 interface between the fourth andfifth wireless communication nodes that the fifth wireless communicationnode assigned to the third wireless communication node, a secondapplication identifier over the F1 interface between the fourth andfifth wireless communication nodes that the fourth wirelesscommunication node assigned to the third wireless communication node,and a flag signal indicative of deleting a context of the third wirelesscommunication node that was stored in the fifth wireless communicationnode.
 13. The method of claim 1, further comprising: when the thirdwireless communication node switches to the radio resource controlinactive mode, receiving a message from an access and mobilitymanagement function of a core network requesting updating a location ofthe third wireless communication node; and sending the location of thethird wireless communication node to the access and mobility managementfunction of the core network, wherein the location of the third wirelesscommunication node comprises at least one of: a cell global identifier,a tracking area identifier, and a random access network notificationarea identifier associated with the third wireless communication node.14. A computing device configured to carry out the method of claim 1.15. A non-transitory computer-readable medium having stored thereoncomputer-executable instructions for carrying out the method of claim 1.16. A method performed by a second wireless communication node,comprising: receiving a first message sent by a first wirelesscommunication node; and passing a first encoded container included inthe first message to a third wireless communication node, wherein thefirst encoded container is configured to switch the third wirelesscommunication node to a radio resource control inactive mode, whereinthe first and second wireless communication nodes cooperate to serve asa first base station in a wireless network, wherein the first messagecomprises at least one of: a suspend message in the first encodedcontainer, a flag signal indicative of deleting a context of the thirdwireless communication node that was stored in the second wirelesscommunication node, a cell-radio network temporary identifier that thesecond wireless communication node assigned to the third wirelesscommunication node, a first application identifier over an F1 interfacebetween the first and second wireless communication nodes that thesecond wireless communication node assigned to the third wirelesscommunication node, a second application identifier over the F1interface between the first and second wireless communication nodes thatthe first wireless communication node assigned to the third wirelesscommunication node, or a signaling radio bearer type, wherein the secondwireless communication node is configured to pass the first encodedcontainer to the third wireless communication node for the thirdwireless communication node to retrieve the suspend signal from thefirst encoded container so as to switch itself to the radio resourcecontrol inactive mode.
 17. The method of claim 16, wherein the secondwireless communication node is a distributed unit of the first basestation, and the first wireless communication node is a centralized unitof the first base station.